1. Field of the Disclosure
The present disclosure relates to a molded case circuit breaker with a large capacity, and particularly, to a molded case circuit breaker capable of reducing an initial operation load without changing a configuration of a switching mechanism, when driving a plurality of movable contact arms for each pole (phase) to a closing position.
2. Background of the Disclosure
A molded case circuit breaker with a large capacity (hereinafter, will be referred to as abbreviated as MCCB with a large capacity) indicates a MCCB capable of increasing a conducting capacity by diverging a conducting path, under a configuration that a plurality of movable contact arms and a plurality of stationary contact arms are provided for each pole of the industrial alternating current (abbreviated as AC hereinafter) three poles (R pole, S pole and T pole) or four poles (R pole, S pole, T pole and N pole).
Korean Patent Registration No. 10-1079012 registered by the applicant of the present invention can be referred to as the conventional art of such MCCB with a large capacity. A MCCB with a large capacity disclosed in Korean Patent Registration No. 10-1079012 has a configuration that a repulsive force to push a plurality of movable contact arms for each pole (phase) to terminals contacting both side surfaces of the movable contact arm is provided by installing disc springs between the movable contact arms. The disc springs are installed in order to stably maintain an electrically-connected state between the movable contact arms and the terminals due to a mechanical contact state therebetween.
In order to open or close (switch) the conventional MCCB, the movable contact arms should be driven by a force greater than a resultant force of a load of a plurality of contact arms which forms the movable contact arms for poles, and a frictional force between the movable contact arms and the terminals due to an elastic force of the disc springs (4 disc springs for each pole) for maintaining an electrically-connected state between the movable contact arms and the terminals.
A driving force to automatically trip the MCCB with a large capacity is strong elastic energy charged to a trip spring having a large elastic coefficient. More specifically, the driving force by the elastic energy charged to the trip spring is much greater than the resultant force of a load of the plurality of contact arms, and a frictional force between the movable contact arms and the terminals due to an elastic force of the disc springs for maintaining an electrically-connected state between the movable contact arms and the terminals. As a result, there occurs no problem when the conventional MCCB operates to trip.
However, a driving force required to manually operate the MCCB with a large capacity to an opening position or closing position is obtained from a user's manual force to manually rotate a handle of the MCCB with a large capacity. Therefore, the user should manually operate the MCCB with a large capacity, with a force greater than the resultant force.
Especially, in a case where the MCCB with a large capacity is manually operated to a closing position (that is ON position), if a driving force is small, a circuit is not closed. Further, if a manual operation to rotate the MCCB to a closing position, heat may occur from a contact portion due to inferior contact between contacts, and electric power may be unstably supplied to the circuit.